In this paper, we focus on voluntary corporate social responsibility (CSR) disclosure, and we test the extent to which the value relevance of CSR reporting is affected by the appointment of female directors. Using a sample of French listed companies belonging to the SBF 120 index from 2001 to 2011, we control for differences in firm characteristics between firms with and without female board membership by using propensity score matching. Our results show that high CSR reporting is more relevant in terms of market value for firms with gender-diverse boards than for firms with completely male directors. This finding holds when we use the accounting-based performance measures, namely, return on assets (ROA) and return on equity (ROE). We also highlight that engaging an external assurance provider for CSR reporting is value relevant for firms without female directors but not value relevant for firms with female directors, suggesting a substitute relationship between gender-diverse boards and CSR assurance. Our results are stable when we consider the presence of at least two and three female directors.